Lawrence R. Caruana

Oxygen delivery through high-flow nasal cannulae increase end-expiratory lung volume and reduce respiratory rate in post-cardiac surgical patients.

BACKGROUND High-flow nasal cannulae (HFNCs) create positive oropharyngeal airway pressure, but it is unclear how their use affects lung volume. Electrical impedance tomography allows the assessment of changes in lung volume by measuring changes in lung impedance. Primary objectives were to investigate the effects of HFNC on airway pressure (P(aw)) and end-expiratory lung volume (EELV) and to identify any correlation between the two. Secondary objectives were to investigate the effects of HFNC on respiratory rate, dyspnoea, tidal volume, and oxygenation; and the interaction between BMI and EELV. METHODS Twenty patients prescribed HFNC post-cardiac surgery were investigated. Impedance measures, P(aw), ratio, respiratory rate, and modified Borg scores were recorded first on low-flow oxygen and then on HFNC. RESULTS A strong and significant correlation existed between P(aw) and end-expiratory lung impedance (EELI) (r=0.7, P<0.001). Compared with low-flow oxygen, HFNC significantly increased EELI by 25.6% [95% confidence interval (CI) 24.3, 26.9] and P(aw) by 3.0 cm H(2)O (95% CI 2.4, 3.7). Respiratory rate reduced by 3.4 bpm (95% CI 1.7, 5.2) with HFNC use, tidal impedance variation increased by 10.5% (95% CI 6.1, 18.3), and ratio improved by 30.6 mm Hg (95% CI 17.9, 43.3). A trend towards HFNC improving subjective dyspnoea scoring (P=0.023) was found. Increases in EELI were significantly influenced by BMI, with larger increases associated with higher BMIs (P<0.001). CONCLUSIONS This study suggests that HFNCs reduce respiratory rate and improve oxygenation by increasing both EELV and tidal volume and are most beneficial in patients with higher BMIs.

Expert consensus and recommendations on safety criteria for active mobilization of mechanically ventilated critically ill adults.

IntroductionThe aim of this study was to develop consensus recommendations on safety parameters for mobilizing adult, mechanically ventilated, intensive care unit (ICU) patients.MethodsA systematic literature review was followed by a meeting of 23 multidisciplinary ICU experts to seek consensus regarding the safe mobilization of mechanically ventilated patients.ResultsSafety considerations were summarized in four categories: respiratory, cardiovascular, neurological and other. Consensus was achieved on all criteria for safe mobilization, with the exception being levels of vasoactive agents. Intubation via an endotracheal tube was not a contraindication to early mobilization and a fraction of inspired oxygen less than 0.6 with a percutaneous oxygen saturation more than 90% and a respiratory rate less than 30 breaths/minute were considered safe criteria for in- and out-of-bed mobilization if there were no other contraindications. At an international meeting, 94 multidisciplinary ICU clinicians concurred with the proposed recommendations.ConclusionConsensus recommendations regarding safety criteria for mobilization of adult, mechanically ventilated patients in the ICU have the potential to guide ICU rehabilitation whilst minimizing the risk of adverse events.

End-expiratory lung volume recovers more slowly after closed endotracheal suctioning than after open suctioning: A randomized crossover study

PURPOSE Endotracheal suctioning causes significant lung derecruitment. Closed suction (CS) minimizes lung volume loss during suction, and therefore, volumes are presumed to recover more quickly postsuctioning. Conflicting evidence exists regarding this. We examined the effects of open suction (OS) and CS on lung volume loss during suctioning, and recovery of end-expiratory lung volume (EELV) up to 30 minutes postsuction. MATERIAL AND METHODS Randomized crossover study examining 20 patients postcardiac surgery. CS and OS were performed in random order, 30 minutes apart. Lung impedance was measured during suction, and end-expiratory lung impedance was measured at baseline and postsuctioning using electrical impedance tomography. Oximetry, partial pressure of oxygen in the alveoli/fraction of inspired oxygen ratio and compliance were collected. RESULTS Reductions in lung impedance during suctioning were less for CS than for OS (mean difference, -905 impedance units; 95% confidence interval [CI], -1234 to -587; P < .001). However, at all points postsuctioning, EELV recovered more slowly after CS than after OS. There were no statistically significant differences in the other respiratory parameters. CONCLUSIONS Closed suctioning minimized lung volume loss during suctioning but, counterintuitively, resulted in slower recovery of EELV postsuction compared with OS. Therefore, the use of CS cannot be assumed to be protective of lung volumes postsuctioning. Consideration should be given to restoring EELV after either suction method via a recruitment maneuver.

Speaking valves in tracheostomised ICU patients weaning off mechanical ventilation - do they facilitate lung recruitment?

BackgroundPatients who require positive pressure ventilation through a tracheostomy are unable to phonate due to the inflated tracheostomy cuff. Whilst a speaking valve (SV) can be used on a tracheostomy tube, its use in ventilated ICU patients has been inhibited by concerns regarding potential deleterious effects to recovering lungs. The objective of this study was to assess end expiratory lung impedance (EELI) and standard bedside respiratory parameters before, during and after SV use in tracheostomised patients weaning from mechanical ventilation.MethodsA prospective observational study was conducted in a cardio-thoracic adult ICU. 20 consecutive tracheostomised patients weaning from mechanical ventilation and using a SV were recruited. Electrical Impedance Tomography (EIT) was used to monitor patients’ EELI. Changes in lung impedance and standard bedside respiratory data were analysed pre, during and post SV use.ResultsUse of in-line SVs resulted in significant increase of EELI. This effect grew and was maintained for at least 15 minutes after removal of the SV (p < 0.001). EtCO2 showed a significant drop during SV use (p = 0.01) whilst SpO2 remained unchanged. Respiratory rate (RR (breaths per minute)) decreased whilst the SV was in situ (p <0.001), and heart rate (HR (beats per minute)) was unchanged. All results were similar regardless of the patients’ respiratory requirements at time of recruitment.ConclusionsIn this cohort of critically ill ventilated patients, SVs did not cause derecruitment of the lungs when used in the ventilator weaning period. Deflating the tracheostomy cuff and restoring the airflow via the upper airway with a one-way valve may facilitate lung recruitment during and after SV use, as indicated by increased EELI.Trial registrationAnna-Liisa Sutt, Australian New Zealand Clinical Trials Registry (ANZCTR). ACTRN: ACTRN12615000589583. 4/6/2015.

Lung Volume Changes During Cleaning of Closed Endotracheal Suction Catheters: A Randomized Crossover Study Using Electrical Impedance Tomography

BACKGROUND: Airway suctioning in mechanically ventilated patients is required to maintain airway patency. Closed suction catheters (CSCs) minimize lung volume loss during suctioning but require cleaning post-suction. Despite their widespread use, there is no published evidence examining lung volumes during CSC cleaning. The study objectives were to quantify lung volume changes during CSC cleaning and to determine whether these changes were preventable using a CSC with a valve in situ between the airway and catheter cleaning chamber. METHODS: This prospective randomized crossover study was conducted in a metropolitan tertiary ICU. Ten patients mechanically ventilated via volume-controlled synchronized intermittent mandatory ventilation (SIMV-VC) and requiring manual hyperinflation (MHI) were included in this study. CSC cleaning was performed using 2 different brands of CSC (one with a valve [Ballard Trach Care 72, Kimberly-Clark, Roswell, Georgia] and one without [Portex Steri-Cath DL, Smiths Medical, Dublin, Ohio]). The maneuvers were performed during both SIMV-VC and MHI. Lung volume change was measured via impedance change using electrical impedance tomography. A mixed model was used to compare the estimated means. RESULTS: During cleaning of the valveless CSC, significant decreases in lung impedance occurred during MHI (−2563 impedance units, 95% CI 2213–2913, P < .001), and significant increases in lung impedance occurred during SIMV (762 impedance units, 95% CI 452–1072, P < .001). In contrast, cleaning of the CSC with a valve in situ resulted in non-significant lung volume changes and maintenance of normal ventilation during MHI and SIMV-VC, respectively (188 impedance units, 95% CI −136 to 511, P = .22; and 22 impedance units, 95% CI −342 to 299, P = .89). CONCLUSIONS: When there is no valve between the airway and suction catheter, cleaning of the CSC results in significant derangements in lung volume. Therefore, the presence of such a valve should be considered essential in preserving lung volumes and uninterrupted ventilation in mechanically ventilated patients.

Head-of-Bed Elevation Improves End-Expiratory Lung Volumes in Mechanically Ventilated Subjects: A Prospective Observational Study

BACKGROUND: Head-of-bed elevation (HOBE) has been shown to assist in reducing respiratory complications associated with mechanical ventilation; however, there is minimal research describing changes in end-expiratory lung volume. This study aims to investigate changes in end-expiratory lung volume in a supine position and 2 levels of HOBE. METHODS: Twenty postoperative cardiac surgery subjects were examined using electrical impedance tomography. End-expiratory lung impedance (EELI) was recorded as a surrogate measurement of end-expiratory lung volume in a supine position and at 20° and then 30°. RESULTS: Significant increases in end-expiratory lung volume were seen at both 20° and 30° HOBE in all lung regions, except the anterior, with the largest changes from baseline (supine) seen at 30°. From baseline to 30° HOBE, global EELI increased by 1,327 impedance units (95% CI 1,080–1,573, P < .001). EELI increased by 1,007 units (95% CI 880–1,134, P < .001) in the left lung region and by 320 impedance units (95% CI 188–451, P < .001) in the right lung. Posterior increases of 1,544 impedance units (95% CI 1,405–1,682, P < .001) were also seen. EELI decreased anteriorly, with the largest decreases occurring at 30° (−335 impedance units, 95% CI −486 to −183, P < .001). CONCLUSIONS: HOBE significantly increases global and regional end-expiratory lung volume; therefore, unless contraindicated, all mechanically ventilated patients should be positioned with HOBE.

Electrical impedance tomography in the clinical assessment of lung volumes following recruitment manoeuvres

Abstract Background: Mechanical ventilation has dramatically improved outcomes in critically ill patients with respiratory failure. Minimizing volumes and higher positive end-expiratory pressures can further improve patient outcomes. Recruitment manoeuvres which can be used to individualize positive end-expiratory pressure may not improve outcome unless recruitable tissue is present. Existing methods of assessing if lung tissue is recruitable have a variety of limitations. Electrical impedance tomography (EIT) is a new technology that may be able to assess whether or not lung tissue is recruitable at the bedside. Objectives: This review will assess the growing body of evidence that EIT is a promising technique which may help the clinician to optimize ventilation, while minimizing injury. We will review how the device works, the data supporting its use, and potential uses for the physical therapist in the critical care environment. Major findings: EIT is a technique of injecting current through tissue, and measuring the difference between an array of electrodes. The difference relates to the changes of volume within the chest cavity – either blood or gas. It is reproducible, non-radiative, and real-time – allowing immediate and repeated imaging in the sickest of patients, who may require high levels of peep and recruitment manoeuvres. Conclusions: This paper has demonstrated that with an understanding of the strengths and limitations of the device, EIT can be used successfully at the bedside by clinicians to guide recruitment and other clinical techniques.

Ventilation distribution and lung recruitment with speaking valve use in tracheostomised patient weaning from mechanical ventilation in intensive care

Purpose Speaking valves (SV) are used infrequently in tracheostomised ICU patients due to concerns regarding their putative effect on lung recruitment. A recent study in cardio‐thoracic population demonstrated increased end‐expiratory lung volumes during and post SV use without examining if the increase in end‐expiratory lung impedance (EELI) resulted in alveolar recruitment or potential hyperinflation in discrete loci. Materials and methods A secondary analysis of Electrical Impedance Tomography (EIT) data from a previous study was conducted. EELI distribution and tidal variation (TV) were assessed with a previously validated tool. A new tool was used to investigate ventilated surface area (VSA) and regional ventilation delay (RVD) as indicators of alveolar recruitment. Results The increase in EELI was found to be uniform with significant increase across all lung sections (p < 0.001). TV showed an initial non‐significant decrease (p = 0.94) with subsequent increase significantly above baseline (p < 0.001). VSA and RVD showed non‐significant changes during and post SV use. Conclusions These findings indicate that hyperinflation did not occur with SV use, which is supported by previously published data on respiratory parameters. These data along with obvious psychological benefits to patients are encouraging towards safe use of SVs in this critically ill cardio‐thoracic patient population. Trial registration: Anna‐Liisa Sutt, Australian New Zealand Clinical Trials Registry (ANZCTR). ACTRN: ACTRN12615000589583. 4/6/2015. HighlightsUniform increase of end‐expiratory lung volume across ventral‐dorsal and R‐L lung sections with speaking valve use.Data suggests no alveolar hyperinflation associated with speaking valve use.Data are encouraging towards wide use of speaking valves in intensive care.

Single-Lung Transplant Results in Position Dependent Changes in Regional Ventilation: An Observational Case Series Using Electrical Impedance Tomography

Background. Lung transplantation is the optimal treatment for end stage lung disease. Donor shortage necessitates single-lung transplants (SLT), yet minimal data exists regarding regional ventilation in diseased versus transplanted lung measured by Electrical Impedance Tomography (EIT). Method. We aimed to determine regional ventilation in six SLT outpatients using EIT. We assessed end expiratory volume and tidal volumes. End expiratory lung impedance (EELI) and Global Tidal Variation of Impedance were assessed in supine, right lateral, left lateral, sitting, and standing positions in transplanted and diseased lungs. A mixed model with random intercept per subject was used for statistical analysis. Results. EELI was significantly altered between diseased and transplanted lungs whilst lying on right and left side. One patient demonstrated pendelluft between lungs and was therefore excluded for further comparison of tidal variation. Tidal variation was significantly higher in the transplanted lung for the remaining five patients in all positions, except when lying on the right side. Conclusion. Ventilation to transplanted lung is better than diseased lung, especially in lateral positions. Positioning in patients with active unilateral lung pathologies will be implicated. This is the first study demonstrating changes in regional ventilation, associated with changes of position between transplanted and diseased lung.

Corrigendum to “Ventilation distribution and lung recruitment with speaking valve use in tracheostomised patient weaning from mechanical ventilation in intensive care” [Journal of Critical Care 40 (2017) 164–170]

The authors regret to inform that Graphs 2 and 3 on page 168 are swapped in the article. The graph headings and written information about the results are all accurate, however graph 3 is in fact graph 2 and vice versa. The authors would like to apologise for any inconvenience caused.